This build is for a friend so just ignore it.
SECURING LAST HITS
Get a salve via courier if the lane is rough.
Bracer for health and 6 dmg will help with last hits.
Band of Elvenskin will also give 6 dmg and almost 1 armour.
With those two items and a Quelling Blade, you should no longer miss last hits.
INCREASING YOUR MOVEMENT SPEED
After every blink you will have to chase the enemy anyway, so instead of more points in blink, we go for movespeed then attackspeed. We will try to max blink by the time we get our yasha however, to stay alive and to gank. Speed also helps you farm everything faster.
Boots of Speed is obviously the cheapest speed increase.
Drum of Endurance is a nice extension of Bracer, so for 1200 g you can buy this for a permanent 5% movespeed, great stats, and burst movement and attack speeds. Overall, during a burst this item is giving you 15% movespeed and 24 attack speed, which is amazing.
Yasha gives 10% movespeed, 26 attack speed, 16 damage and 2 armour, which helps you farm creeps significantly in addition to further increasing your ganking potential.
INCREASING YOUR ATTACK SPEED
Power Treads is a super cheap way of getting 30 attack speed and tread switching before and after blink will allow you to farm both the lane and the jungle faster.
Manta Style does not increase your personal attack speed by much, but the ultimate orb is useful and having two illusions also use mana break will drain an enemy's mana to 0 in no time. The illusions are super fast with drums, and therefore potentially allow you to triple your mana drain rate. Then you can use your ultimate on a hero with no mana.
Get 3 or 4 points in Mana Break by the time you get Manta Style
SITUATIONAL CORE INSERTS
If you just save your mana except when you need to gank, perseverance will not be necessary. Moreover, Battle Fury is just a farming item for AM (you don't really need the damage, the cleave or the hp and mp regen to carry a team fight) and if you can farm decently well without getting it, you will be of much greater assistance to your team in the early- and mid-game. Otherwise, AM is a pretty big burden on the rest of his team, as he does need babysitting in the lane no matter what, and cannot be a major contribution to the team's struggles until he can get a second big item. Drums are cheap and a Manta Style turns you into a mana-draining, nuking machine, while a battle fury makes you only slightly better at farming than drums/yasha/treads. Oh, and Poor Man's Shield is good for exactly when it says it is: when you are poor. If you are doing well you don't get it as you may have to sell both your quelling blade and your shield soon to make space. It scales horribly too and you are a carry. Hood of Defiance stacks with Spell Shield, making you almost invulnerable to magic damage, and is a great substitute for bfury's hp regen, further allowing you to skip that item.
That's it for your core. You can get farmed either by ganking (start after getting drums)or by farming the nearest creeps. Then the Situational are really a matter of preference and circumstances.